Heating of zinc ovens



July 16, 1963 A. A. J. QUINTIN HEATING OF ZINC OVENS Filed April 21,1961 I Sl I I i Q lilll United States atent 3,097,835 Patented July 16,1963 free 3,097,835 HEATING OF ZINC OVENS Albert Andr Joseph Quintin,Overpelt, Belgium, assignor to Compagnie des Metaux dGverpeit-Lommel ettie Corphalie, S.A., Overpelt-lez-Neerpelt, Belgium Filed Apr. 21, 1961,Scr. No. iiMJlil Claims priority, application Great Britain June 14, W696 Claims. (Cl. 263--37) This invention relates to the heating of zincovens by means of liquid fuel,

For heating metallurgical furnaces with liquid fuel, use is generallymade of extra-heavy liquid fuel, which is least expensive. Owing to itsviscosity when cold, such liquid fuel has to be heated before it isintroduced into the combustion chamber of the furnace, and is admittedin a finely-divided form obtained by pulverization by means of steam orair under pressure, or by means of mechanical pulverizing devices. Forapplying such a process, the furnace should have a combustion chamber ofa capacity and shape such that at no moment shall any pulverized liquidfuel come into contact with the surfaces to be heated. Otherwise, acracking takes place and carbon in a form difficult to burn, isdeposited upon the surface of the furnace, on which it hardens; suchhard deposits grow rapidly and disturb the passage of the flames andthus the good working of the furnace.

When the combustion chamber of the furnace has in at least one directionsmall dimensions, for instance when it is obstructed by the objects tobe heated, as is the case for instance with zinc ovens with multipleretorts, which generally are heated by means of gas (producer gas,natural gas, etc.) the difficulty may be avoided more or lesssatisfactorily by gasifying the liquid fuel outside the cost ofconstruction, and leads to losses of heat.

The present invention consists in a process for heating the furnace inapparatus in which it is subjected to high temperatures. Such anarrangement however increases zinc ovens having a plurality of rctortswith liquid fuel such as heavy fuel oil which consists in injectingthin, non pulverized jets of said fuel between the retorts so that underthe combined effect of the contact with the incandescent gases and ofthe radiation of the hot sur faces the liquid fuel is totally vaporizedbefore it can strike a solid surface and form carbonaceous deposits.

The vapours thus produced are inflamed and ensure by their combustionthe heating of the combustion chamber. Such an arrangement avoids allgasifying arrangement outside the combustion chamber and consequentlyimportant losses of heat, excessive size. It represents a greatsimplification of plant and ensures a maximum yield of heat, since thetotality of the heat contained by the fuel is liberated inside thecombustion chamber where it is utilized.

Generally zinc ovens have horizontal retorts, are heated with producergas or natural gas, and work with periodical reversal of the gas and airinlets. In such ovens the space between the retorts is small.

According to one feature of the present invention the liquid fuel isinjected in a downward direction into the spaces between the verticalrows of retorts, preferably in the direction of a vertical plane passingthrough the uprights supporting the roof of the oven, where owingprecisely to the presence of the upright, there is a space between thevertical rows of retorts which is just sufficient for such injection.

The diameter of the streams of liquid and the speed of their injectionare such that the gasifying process is achieved at the level of thelower row of retorts and no liquid fuel reaches the floor of the zincovens, thus avoiding its cracking and all production of hardened carbon.

The streams of liquid fuel travel thus in an opposite direction to thatof the combustion air which is heated in the regenerators, rises in anupward direction and brakes to a certain extent the speed of the thinstreams of. liquid fuel whilst becoming mixed with the vapours of liquidfuel, and the latter is immediately lighted.

In order to completely vaporize the fuel before the latter reaches thefloor where the air is subdivided, the injection of fuel is generallysubdivided in the vertical plane of the uprights of the oven into two orseveral jets of a small diameter, for instance comprised between abouthalf a millimetre and about one millimetre. Such jets may have differentdiameters and directions, they may be even oblique, the main objectbeing to ensure a regular conversion into vapour and combustion of theliquid fuel along the entire height of the oven, at its various levels,thus rendering the temperatures uniform. In certain cases, in order toobtain uniform temperatures along the entire height of the oven withoutliquid fuel reaching the floor of the oven, it may be advantageous toinject a small portion of fuel gas into the oven at its lower level,together with the combustion air, thus ensuring an additional heating atthe lower level of the retorts, allowing thus to reduce the length ofthe streams of liquid fuel. Such an injection of gas may advantageouslybe made by using carbon monoxide (CO) as the gas, and namely the carbonmonoxide gas which escapes from the rctorts. Such gas may be collectedin any convenient manner.

When the direction of gases in the oven is to be reversed, that isgenerally every 15 to 30 minutes, the inlet of liquid is closed for onehalf of fuel injecting devices in operation on half the oven, theadmission of air is reversed, and the liquid fuel is admitted to theother half of injecting devices, this latter half receiving now thecombustion air which has been heated in the regenerators.

Such a heating arrangement with multiple injections of liquid fuel atdifferent points of the zinc oven, allows of more regularly heating thanwhat is generally obtained with a gaseous fuel. It is indeed sufficientto provide a flow meter and a throttle valve for each injector in orderto maintain the required amount of fuel for each injector. It is alsopossible to provide for each injection a small pump of variable outputremaining strictly constant for each position of the regulating device.

In the heating arrangement of zinc ovens above described, the injectingdevices for liquid fuel placed on the roof of the oven above the narrowpassages provided in the masonry, which allow a passage to the streamsof liquid fuel, are subjected to radiation from the combustion chamberthrough the said passages during the period for which they deliverliquid fuel, and also during the period for which they are not working,when passing from one reversal to another. An overheating of theinjector and therefore of the liquid fuel, should be prevented in orderto avoid cracking and thus obstructions. For that purpose, a cooling ofthe injector may be ensured by a flow of liquid and by a thin curtain ofwater droplets provided between the injector and the passage in theroof, obtained for instance by injecting wet saturated water vapour. Itis obvious that during the period for which the injectors do not work,it is also possible to provide a flap valve made of a material which isnon-conductive of heat and resists well to the action of heat, whichautomatically closes the passage in the roof and protects the injectingdevice from heat radiated by the oven.

One of the advantages of the persent invention is that it may be readilyapplied at little cost to zinc ovens working with reversals, and heatedwith combustible gas. The heating arrangement by gas may be retained topass from liquid fuel heating to gas heating, when liquid fuel is nolonger available.

FIGURES I to 3 of the accompanying drawings show a mode of applying theinvention to a Zinc oven with 4 rows of retorts of the type working withreversals.

FIGURE 1 is a vertical section made in a zinc oven by a planeperpendicular to the partitioning wall which divides the ovenlongitudinally in halves. The numeral 1 shows the said partitioningwall; the reference numerals 2, 2 show retorts which are supported atthe rear into recesses provided in the wall, the numeral 3 shows theroof of the oven, the numerals 21, 21 show heat regenera tors withlattice-work packings, the numerals 4, 4 show pipes through whichcombustion air heated in the regenerators is introduced into thecombustion chamber of the oven, whilst liquid fuel is injected into thecorresponding half-oven, and through which leave the hot gases producedby the combustion of liquid fuel during the period which follows thereversal.

FIGURE 2, which is a view of the front wall of the oven, shows uprights17, supporting plates 18 upon which are supported the front part of theretorts 2, the axial lines AA and BB showing the position of the axes ofthe uprights and of the openings or passages 5 shown in FIGURE 1.

The said axial lines show also the position of the injector shown inFIGURE 3.

The FIGURE 3 shows a section made in the arrangement for the injectionof liquid fuel, along a vertical plane parallel to the partitioning walland passing through the axis of a vertical injector.

A horizontal metal flooring of lattice-work formation not shown in thedrawings, may be provided above the roof of the oven. It SBI'VEES forthe suspension of the casings of fuel injecting devices and for thecirculation of the workmen who supervise and maintain the arrangement ingood working order.

The numeral 7 shows a casing with two boxes 8 and 9, cooled by a waterflow. The water is brought by conduits 8' and 9', and leaves throughconduits 8" and 9". Wet saturated water vapor is brought through aconduit 20 to the pipe 10 provided with orifices 11 through which thewater vapour escapes and forms a veil of vapours underneath theinjectors 13.

The numeral 12 shows a supporting block for the injectors 13 which arescrewed into the mas of the supporting block, the orifices 14 of theinjectors projecting thin jets of liquid fuel through the roof of theoven.

The numeral 15 shows a conduit for bringing in the liquid fuel and thenumeral 16 shows a channel for its distribution to the various injectorsbelonging to one and the same block. Each block comprises preferablyseveral injectors of different diameters.

The various blocks are arranged above the passage 5 provided in the roof3 of the oven and the supports are fixed to the above mentioned metalflooring, by means of girders 6, 6.

The block 12 is made independent from the casing 7. It rests upon themachined and horizontal bearing surface 19. A sand joint 22 ensures ifnecessary, a tight joint.

It is thus possible to supervise the injectors in a rapid and easymanner, whilst avoiding all disturbance of the direction of the jets ofliquid fuel, when the supporting blocks are removed or replaced inposition.

The water cooling of the boxes 8 and 9 and the ad mission of wetsaturated water vapour protects the injectors against any undesirableheating due to heat radiation from the combustion chamber, and protectsthe entire arrangement against any deformations produced by an excessiveheating.

The above arrangement more particularly prevents an overheating of theliquid fuel which remains stationary ell) during the period ofnon-injection and also prevents the ensuing cracking, as the watervapour prevents any excessive cooling which would solidify the liquidfuel and would make a rc-starting of the injection uncertain.

What i claim is:

l. A process for heating zinc ovens having an enclosure in which aplurality of retorts is provided between which incandescent gases passwhich heat the surfaces of the retorts, which comprises movingcombustion air in an upward direction between the retorts, whileinjecting liquid fuel in a downwards direction between the retorts injets, controlling the diameter of the jets of liquid fuel and the speedof the jets to allow the liquid fuel to be substantially completelyconverted into vapor state under the combined effect of the contact withthe incandescent guses and of radiation of the hot surfaces of theretorts before they reach the floor of the oven, thus avoidingcarbonaceous deposits upon the inner surface of the oven or the retorts.

Z. A process for heating zinc ovens having an enclosure in which aplurality of retorts is provided between which incandescent gases passwhich heat the surfaces of the retorts, which comprises movingcombustion air in an upward direction between the retorts whileinjecting liquid fuel in a downwards direction in jets of between abouthalf a millimeter and about one millimeter diameter controlling thespeed of the jets to effect conversion of the liquid fuel, into vaporstate under the combined effect of the contact with the incandescentgases and of radiation of the hot surfaces of the retorts before theyreach the floor of the oven, thus avoiding carbonaceous deposits uponthe inner surfaces of the oven or the retorts.

3. A zinc oven having an enclosed casing with a roof, a floor and walls,a plurality of retorts inside the casing supported on the walls, meansfor supporting the retorts inside the casing, uprights arranged in aplane for supporting the roof, means for causing combustion air to passupwards between the retorts and for causing incandescent gases formed inthe oven to pass between the retorts to heat the surfaces of theretorts, and downwardly directed means arranged upon the roof of theoven for injecting thin jets of liquid fuel in a downward direction intothe oven a sufficient distance into the oven and between said retorts tocause said liquid fuel jets to he completely converted into vapor statebefore they can strike the floor of the oven.

4. A zinc oven as claimed in claim 3, in which the means for injectingthe thin jets of fuel in a downward direction into the oven are arrangedin the plane of the said uprights.

5. A zinc oven as claimed in claim 3, having means associated with saidmeans for injecting liquid fuel for providing a curtain of fine dropletsof Water and steam protecting the means for injecting liquid fuelagainst radiation from the oven.

6. A Zinc oven as claimed in claim 3, having superimposed parallel.horizontal rows of retorts, and means for heating the lowest row ofretorts with carbon monoxide gas which escapes from the interior of theretorts.

References Cited in the file of this patent UNITED STATES PATENTS 612104Hegeler Oct. ll, 1898 876,891 Ziesing Jan. 14, 1908 893,560 Ziesing July14, 1908 1,048,420 Londress et al Dec. 24, 1912 2,386,429 Breyer Oct. 9,1945

1. A PROCESS FOR HEATING ZINC OVENS HAVING AN ENCLOSURE IN WHICH APLURALITY OF RETORTS IS PROVIDED BETWEEN WHICH INCANDESCENT GASES PASSWHICH HEAT THE SURFACES OF THE RETORTS, WHICH COMPRISES MOVINGCOMBUSTION AIR IN AN UPWARD DIRECTION BETWEEN THE RETORTS, WHILEINJECTING LIQUID FUEL IN A DOWNWARDS DIRECTION BETWEEN THE RETORTS INJETS, CONTROLLING THE DIAMETER OF THE JETS OF LIQUID FUEL AND THE SPEEDOF THE JETS TO ALLOW THE LIQUID FUEL TO BE SUBSTANTIALLY COMPLETELYCONVERTED INTO VAPOR STATE UNDER THE COMBINED EFFECT TO THE CONTRACTWITH THE INCANDESCENT GASES AND OF RADIATION OF THE HOT SURFACES OF THERETORTS BEFORE THEY REACH THE FLOOR OF THE OVEN, THUS AVOIDINGCARBONACEOUS DEPOSITS UPON THE INNER SURFACE OF THE OVEN OR THE RETORTS.